Electric heaters wherein a support and mounting assembly supports a plurality of insulators for a helical heating element are shown in U.S. Pat. Nos. 5,329,098 (Howard et al.), 5,324,919 (Howard et al.) and 4,617,547 (Howard et al.). In these patents, there are several types of heater support and mounting assemblies shown. Generally, these assemblies comprise a support element, for holding and supporting the insulators, mounted within a housing. The housing is generally a continuous U-shaped sheet of material designed to serve as a portion of the air duct in which the heater is to be inserted.
These patents depict and describe a variety of ways known in the art for attaching the support element to the housing. The heater support and mounting assembly in U.S. Pat. Nos. 5,329,098 and 5,324,919 show the support element having projections which are inserted and extend through slots in the sidewalls of the housing. U.S. Pat. No. 4,617,547 shows an assembly where the support element has protruding down-turned rods which are received by projections along the outside edge of the housing. Some other ways of attaching the support element to the housing discussed in these patents include welding or riveting.
The problem with the support and mounting assemblies heretofore is that the support element was either rigidly affixed to the housing or loosely inserted into a portion of the housing. The support element provides support for the insulators which, in turn, support the electric heating element. The current running through the electric heating element induces a vibration in the support and mounting assembly that results in a noise, for instance a rattle or chatter, at any loose fitting connection. This noise has been a persistent problem for electric heaters wherein the support element is loosely inserted in a slot within the housing. This problem can be overcome by welding or riveting the support element to the housing. However, when the support element is rigidly affixed to the housing this reduces the assembly's ability to accommodate thermal expansion, particularly, in the support element which results in stresses in the support element and/or housing.
Therefore, there is a need for an electric heater support and mounting assembly that holds the support element in a manner that minimizes noise associated with vibration of the heating element while allowing the support element to move within the housing to relieve stresses resulting from thermal expansion.
Another concern in the design and manufacture of an electric heater support and mounting assembly is the number of parts and the expediency of the overall assembly process. Assemblies that require numerous parts generally require additional assembly steps and cost more than those utilizing fewer parts. Therefore, there is a need to provide an electric heater support and mounting assembly that can readily be assembled and has a minimum number of components.
Accordingly, it is an object of the present invention to provide an electric heater support and mounting assembly having a plurality of joints each comprising an opening in a mounting element for receiving and firmly holding a portion of a support element in a manner that reduces or prevents the support element from rattling or chattering within the opening while allowing the inserted portion of the support element to move within the opening to accommodate thermal expansion of the support element.
It is another object of the present invention to provide an electric heater support and mounting assembly having a plurality of joints each comprising an opening having a tension member which forces an arm of a support element extended through the opening against a side of the opening and thereby substantially reducing or preventing the arm from rattling or chattering within the opening.
It is still a further object of the present invention to provide an electric heater support and mounting assembly having a joint consisting essentially of an opening within a housing formed by removing material from the housing and a protruding member of a support element extending through the opening whereby the protruding member is able to move within the opening but is prevented from vibrating against the side of the opening.